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Full Version: Does the HP-IL module for the HP-41C break the loop?
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does the HP-IL module for the HP-41C break the loop when it is unplugged or the HP-41C is powered off?

I have a HP-IL device with a built-in HP-41C IL-Module. Since I know nothing about the device, I want to hook up a HP-71B to get the device id using DEVID$(1). Simply connected (via the 2 cables, so the loop should be complete with just these three devices [HP-71B, device, HP-IL module]) to the device, the HP-71B takes a long time (about 30 seconds), then displays "HP-IL Error: loop broken". Is this because the IL-module does not close the loop if the HP-41C is turned off?

I have a HP-41CX for using the device, however, I don't see how I could obtain any information about the device without the IL-extension module or the I/O module. So I want to try it with the HP-71B.

Yes. AFAIK, all of the HP products using HP-IL break the loop when they are powered down. Some of them have a standby state in which loop activity will wake them up, but until they have awakened the loop is broken.

The 41 also "breaks the loop" when you have it in the loop with another controller (e.g., 71B), because the 41 doesn't support multiple loop controllers. (Exception - when you use the HP-IL development module to make the 41 act as a loop monitor only.)